1. Field of the Invention
This invention relates to an improved pneumatically operated heat exchanger system and a self-contained control unit therefor as well as to methods of making such a system and such a control unit.
2. Prior Art Statement
It is known to provide a pneumatically operated system having a control unit provided with a single inlet for being interconnected to a one pressure level pneumatic source and having outlet means interconnected to pneumatically operated heating and cooling heat exchanger means to control the same in either its heating mode or its cooling mode in relation to the pressure value of the pneumatic signal means being directed thereto from the control unit through the outlet means thereof, the control unit having temperature sensing means for controlling the value of the signal means in relation to the sensed output temperature effect of the heat exchanger means by operating bleed means of the control means. Such prior known pneumatically operated heat exchanger system either utilizes two temperature sensors and two outlets on the control unit with a single pressure level source or one temperature sensor and one outlet on the control unit with a two pressure level pneumatic source, one pressure level operating during the cooling mode and the other pressure level operating during the heating mode.
For example of the last-mentioned prior known arrangement, see the U.S. Patent to Puster et al, U.S. Pat. No. 3,819,113.
The U.S. Patent to Puster et al, U.S. Pat. No. 3,819,113, also illustrates in FIG. 1 thereof a pneumatically operated system of the above type wherein a single pressure level source is utilized and only one outlet is provided therefor. In addition, a single temperature sensor is provided for the control system. However, the control system must have the bimetal member thereof physically turned over when the system is being converted from its heating mode to its cooling mode or being changed from its cooling mode to its heating mode.
Applicant is also aware of a control that has one outlet and uses a single pressure level pneumatic source for operating the heat exchanger means except that the control device has two separate temperature sensors, one sensor for controlling the cooling mode and the other sensor for controlling the heating mode.